Basically in form and function, they are the same: a heavy top with a thick collar for throwing and wrestling, pants typically with reinforced knees for wrestling, and a belt for keeping the top closed as well as being an extra hand hold.
At a beginner training and competition level, the use of either jiu-jitsu kimono or judo gi is mutually exclusive, it's the uniform that you get beat in -- A LOT! Jiu-jitsu tournaments are more poorly organized than judo, so a proper judo uniform is necessary for competition but jiu-jitsu kimonos fall in this category.
From what I have observed, it seems like the judo uniform sleeves can be worn higher and tighter than in jiu-jitsu. The jiu-jitsu kimonos have thicker lapels on average and are built to withstand the rigors of groundfighting. Judo gi's usually have a two piece cut, while jiu-jitsu has a one or two piece cut.